More than 100 crop varieties were on display at this year's Sunbelt Expo Field Day — held July 8, in Moultrie, Ga. — and those in attendance received updates on everything from rethinking peanut seeding rates to refining the window for treating stinkbugs in cotton.
“The University of Florida, the University of Georgia and USDA keep releasing new peanut varieties, and we need to keep comparing them,” says University of Georgia Extension peanut specialist John Beasley. “We have 15 cultivars planted at the Expo site.”
Peanut row-pattern evaluations have been conducted each year since 1986, says Beasley. “This is the first year we've been able to look at twin and single rows of new cultivars such as Georgia 7W, Georgia Greener, Florida 07, McCloud, AP-4, York and TifGuard,” he says.
At four locations this year, the 15 varieties featured at the Expo also are being evaluated on the basis of the planting date, says Beasley. “Many producers want to go back and plant these cultivars earlier, maybe in mid- to late-April as opposed to mid- to late-May. We've been going with the later planting dates due to the threat of tomato spotted wilt virus. We'll see how these varieties respond to the earlier dates,” he says.
Researchers also are looking at a number of different seeding rates for these new peanut cultivars, says Scott Tubbs, University of Georgia cropping systems agronomist. “We've gotten several questions about whether we might be able to back off the recommended seeding rate of six seed per foot of row, or three seed for twin, for some of these new varieties. So we're evaluating some of these new cultivars in twin and single rows to see if we can possibly drop back on those rates and maybe save you on some seed costs or potentially even bump them up for higher yields,” says Tubbs.
This marks the second year of a nutrient cycling study on peanuts and cotton, he adds. “We're looking at how various cover crops break down and provide nutrients back to the soil which in turn provides nutrients to the subsequent crop. We've worked on a sod-based rotation for peanuts — growing peanuts after bahiagrass.
“We're looking at various aspects of that rotation, where we're killing the bahiagrass in the fall or in the spring. We want to see if that has an effect on how peanuts will germinate and grow. In addition, we're looking at two years versus three years of bahiagrass versus standard rotations,” says Tubbs.
Other research involves long-term rotations of cotton-cotton-peanuts, cotton-corn-peanuts, and corn-cotton-peanuts, he says. Conventional and strip-tillage also are being compared in twin and single-row peanuts.
“We've also got studies this year where we're comparing 30-inch row peanuts with 36-inch rows. We're looking at inoculants and starter fertilizer rates on peanuts and how they interact with one another or on their own with the various varieties,” says Tubbs.
As for cotton fertilization, it's back to the basics, says Glen Harris, University of Georgia Extension agronomist. “Fertilizer prices are at an all-time high, so we're looking at ways to still make a good crop — things like soil testing and getting the proper pH,” he says.
The “basics,” says Harris, include looking at the rates of nitrogen, phosphorus and potassium on cotton. “Also, there are several new fertilizer additives that are advertised to make your fertilizer more efficient, and we're looking at those.”
A lot of growers, he says, want to know if they can cut back on fertilizer rates. “It might depend on where you are now. If you were a little over to begin with, you might have a little room. But if you've already cut back to where you need to be, and you cut back further, you'll probably cut your yields,” he says.
Harris also is looking at additives for phosphorus and potassium.
Cotton insect work at the Expo site primarily is focusing on two pests — aphids and stinkbugs, says Phillip Roberts, Extension entomologist.
“In terms of aphid management, we conduct standard efficacy trials each year looking at various insecticides and aphid control, and we do have very good materials to control aphids. Also, we can do it fairly economically. Maybe a more important question is whether or not there is a yield response to aphid control in general. When we look at all our data conducted over the past several years, we cannot see a consistent yield response to controlling aphids. We may have a response every now and then, but it's not consistent,” he says.
Roberts says he'll continue to generate data trying to understand when there is a yield response. “In doing that, we can have different timings or thresholds for treating aphids based on the number of aphids per leaf,” he says.
Two trials at the Expo are looking at stinkbug control, and they are part of a regional project, he says. “One of our objectives with these trials is to understand the critical window of when it is most important that we do a good job of checking cotton for stinkbugs. If you think about how a cotton plant grows and develops, the number of bolls on a plant during any given week that are susceptible to stinkbugs varies.
“During the fourth or fifth week of bloom, you've got a lot of bolls on the plant that are susceptible to stinkbugs. We're continuing to refine when is that critical window when we need to be doing a really good job of controlling stinkbugs. It's somewhere between that third to fifth or sixth week of bloom. That's when we have the most to lose from stinkbugs,” says Roberts.
Researchers also are looking at different types of thresholds for treating stinkbugs, he says. Currently, the threshold for stinkbugs is one boll out of five, or 20 percent, that has been fed on by stinkbugs.
“What we're looking at, is when we have very few bolls susceptible to stinkbugs — like on the tail-end of the year or early in the bloom cycle — of raising that threshold, because you don't have much to lose. When we're in that critical window — that third to fifth week of bloom — we're looking at lowering the threshold. It's common sense if you think about it. In the coming years, you'll hear us start to talk more about something called ‘dynamic thresholds,’ and that may help us do a better job on stinkbugs,” says Roberts.